The 3rd generation mobile communications Long Term Evolution (LTE) system is composed of an Evolved Universal Terrestrial Radio Access Network (E-UTRAN), a User Equipment (UE) and an Evolved Packet Core (EPC). Wherein, the E-UTRAN is composed of an enhanced Node B (eNB) of an access network element. The eNB is connected to the terminal UE through an interface Uu, and it is connected to core network elements such as a Mobility Management Entity (MME) through an interface S1.
Currently, an access network side has multi-layered access control processing mechanisms with respect to access of the user equipment, so as to guarantee that situations such as the overload will not occur at the network side due to the access of excess user equipments.
The user equipment accessing the network side is required to complete a plurality of processes as shown in FIG. 1:
random access process: the user equipment completes the synchronization between the user equipment and network side through the process;
Radio Resource Control (RRC) connection process: it establishes a signalling bearer for the user equipment and access network element; and
Attach process: it completes acquisition of user equipment identifier information, an authentication process and security setup.
In the existing protocol, the network side sets 15 Access Classes (ACs) for different call types, wherein common calls all belong to AC0˜9, emergency calls belong to AC10, and other high priority calls belong to AC11˜15. The network side sets a control factor for the AC0˜9, sets an identifier “Ban or Not” for the AC10 and AC11˜15, and sends the control factor and the identifier to the user equipment, so as to control random access behaviors of these call types.
In the RRC connection process, the signalling interaction between the user equipment and access network element is as shown in FIG. 2 and FIG. 3, and it has two flows: connection establishment flow and connection rejection flow.
Through these two flows, according to information such as data load capacity and signalling load capacity of the network side and air interface load capacity and so on, the network side can make a judgment of “Accept” or “Reject” on a RRC connection request of the user equipment.
Considering that the connection request initiated by the user equipment may be based on various services, and priorities of the services are different, and in order to implement more flexible and effective admission control, in the current RRC layer protocol, the user equipment is required to carry establishment cause information in the RRC connection request.
The existing establishment cause information includes the following contents:
Emergency (it is indicated that the user equipment initiates an emergency call),
High Priority Access (it is indicated that the user equipment initiates a high priority service type call),
mt-Access (it is indicated that the user equipment applies for establishing a connection due to being called),
mo-Signalling (it is indicated that the user equipment initiates a calling signalling type call), and
mo-Data (it is indicated that the user equipment initiates a calling data type call).
The above establishment cause information is only applied to the 3GPP release 9 and the previous version of the user equipment.
With the development of the conception of Internet of Things, Machine to Machine (M2M) communication (called as Machine Type Communication (MTC) in the 3GPP) will be gradually introduced to the whole society. M2M is defined as the machine to machine communication in a narrow sense, and it is defined as networked applications and services with a machine terminal intelligent interaction as the core in a broad sense. Based on an intelligent machine terminal, it uses various communication modes as access means to provide an informationalized solution for clients, which is used to satisfy informatization requirements of the clients on aspects of monitoring, command and dispatch, data acquisition and measurement and so on.
In the M2M applications, the scope of service types is extremely extensive, such as home meter reading, industrial meter manufacture automation, water quality monitoring, intelligent transportation and asset tracking and so on, the M2M applications will enter all walks of life and thousands of households, and the service types of the M2M will also be various, and Quality of Service (QoS) requirements of the network side and operators will also be diverse. The number of user equipments of the M2M will also greatly exceed the number of mobile phones at present, and it will cause enormous pressure of service load to the current and future radio networks. Since the number of user equipments of the M2M is huge, the 3GPP currently put forwards a concept of managing the user equipments in a group way.
Under the background of the M2M applications, how to protect the network and prevent the network from an occurrence of overload becomes a problem required to be solved at present.
In the current protocol, the user equipment can establish a connection to the network through random access, and in the process of completing the attachment, the access network element can perform access control on the random access process and also can perform control on the RRC connection request of the user equipment in the RRC layer, but the flexibility of the current control mechanism cannot satisfy the admission control of high-density and multi-service user equipments any more.
For example, at present, statistical results of the operators show that, the load of data services (such as net surfing, video calls and FTP downloading and so on) in the radio communication has exceeded the load of voice services. When the network faces the overload pressure, an appropriate method is to perform certain admission control on the data services and guarantee the normal service of the voice services since the voice services are generally the foundation of network operation from the perspective of operators. However, according to the current protocol standard, when the user equipment initiates voice calls and data service calls, all the establishment cause information in the RRC connection request is mo-Data, and the network side cannot distinguish whether they are the voice services or the data services, thereby failing to perform flexible admission control.
In addition, different M2M applications have different service models, a service model means a data transmission model during the data interaction between the user equipment and the network side, elements for representing the service model include: data interaction periodicity, data interaction frequency, data size, data interaction direction (i.e. uplink data dominated, or downlink data dominated, or similar uplink traffic and downlink traffic). An intelligent electric meter is taken as an example, certain electric power companies require that each intelligent electric meter report meter reading data once every 5 minutes, certain electric power companies require that each intelligent electric meter report meter reading data once every 1 hour, and certain electric power companies even require that the intelligent electric meter only report meter reading data once every day, and since traffic of the meter reading data at each time is comparatively small, it forms 3 kinds of different service models, which can be respectively called as high frequency periodic small data report, low frequency periodic small data report and extra-low frequency periodic small data report. For another example, a common voice service can be called as an extra-high frequency periodic small data interaction model. For another example, an internet service (generally the webpage is clicked once every dozen of seconds, the downlink data are dominated, and the data traffic is larger) can be called as a medium frequency aperiodic big data download model. These different service models are obviously diverse with respect to the network pressure, but the current mechanism cannot distinguish these service models.
Different services still have different Qos requirements, and the Qos requirements related to the admission control include: access delay tolerance, for example, certain services are extremely sensitive to access delay (such as services including fire alarm, safeguard and medical monitoring and so on), and certain services have a low sensitivity to the access delay (such as meter reading), and the current mechanism cannot distinguish these differences.
Different services or user equipments still have different priorities, such as priorities of services related to finance, safeguard and medical treatment should be higher than priorities of common services, but the current mechanism cannot make a distinction.
After the M2M are widely applied, these defects will become more serious.